1. Technical Field
The present invention relates to granular material feed devices for conveyor belt systems and, more particularly, to a gripping intake system for a dual belt conveyor which includes a hopper for storing granular material adjacent the return sections of the upper and lower loop belts of the dual belt conveyor, a tail roller engaging the upper loop belt between the return section and the conveying section, at least one hold down roller engaging the lower loop belt between the return section and the conveying section such that the upper and lower loop belts are held in spaced apart configuration prior to the conveying sections of the upper and lower loop belts being biased towards one another in face-to-face conveying relationship whereby granular material falling from the hopper comes into contact with the upper and lower loop belts which engage the granular material, accelerate the granular material via gravity and periodic engagement of the granular material with at least one of the upper and lower loop belts and the adjacent accelerated granular material to approximately the same speed as the belts and then feed the accelerated granular material into the dual belt conveyor whereby the granular material is more efficiently fed into the face-to-face conveying relationship section of the dual belt conveyor.
2. Description of the Prior Art
Dual belt conveyor systems similar to U.S. Pat. No. 6,484,870 issued to Bohnker et al. work well to carry granular product up steeper inclines than the angle of repose of that particular product. Once product is squeezed between the two belts, product is conveyed very effectively. However, the intake of the conveyor has proven to be troublesome due to the fact that the conveyor is typically set at an angle which is greater than the angle of repose and a method must be designed to throw product between the belts for the dual belt system to be successful. Currently, there are designs that have been used to transfer product into the dual belts with some success. However, these designs have application restrictions that limit the use of the dual belt system.
An example of one of the current designs is a Horizontal Feeder Conveyor, such as that shown in FIG. 7, which is used to accelerate the product so it can be thrown between dual belts in the conveyor. Disadvantages of this method are:                1. Requires an additional conveyor with an additional drive process.        2. Complicates conveyor as feeder conveyor needs to remain nearly horizontal even as dual belt conveyor increases in angle.        3. Controlling 100% of the granular product is difficult when product is “thrown” into dual belts.        4. Successful application of dual belt conveyor is limited with need of additional feeder conveyor.        5. Making the Dual Best Conveyor portable is complicated as the feeder conveyor changes the center of gravity of the total conveyor. Also, the feeder conveyor pivots independently from the dual belt conveyor, thus the center of gravity is not fixed.        6. Transmitting drive power from the front tail of the conveyor is extremely difficult with the pivoting feeder conveyor in place. Front power drive is of value to enable the conveyor to be portable for some applications.        
Another example is the Elongated and Fixed Leg of Bottom Belt design, which is shown best in FIG. 8, which includes an elongated and fixed bent leg of bottom belt which is used to accelerate granular product at a reduced angle prior to being squeezed between dual belt conveyor. Again, however, improvements are needed because:                1. Angle is fixed limiting use of conveyor to angle of repose of granular product on the elongated leg.        2. Efficiency of conveyor is dependent on angle of repose of product, changes by product conveyed.        3. Efficiency of conveyor is also dependent on success of top belt to squeeze product as angle of incline is increased.        
Therefore, an object of the present invention is to provide an improved gripping intake system for use with a dual belt conveyor.
Another object of the present invention is to provide an improved gripping intake system for use with a dual belt conveyor which includes a hopper which feeds the granular product into the gap between the upper and lower loop belts which allows the belts themselves to accelerate the product prior to sandwiching of the product between the belts within the dual belt conveyor.
Another object of the present invention is to provide an improved gripping intake system for use with a dual belt conveyor which includes a plurality of hold down rollers which hold the lower loop belt in spaced apart configuration from the upper loop belt in order to provide an entry chute into the gripping intake system for the granular product.
Another object of the present invention is to provide an improved gripping intake system for use with a dual belt conveyor which will quickly and safely accelerate granular product to the approximate speed of the upper and lower loop belts to facilitate intake of the granular product into the dual belt conveyor.
Finally, an object of the present invention is to provide improved gripping intake system for use with a dual belt conveyor which is relatively simple and durable in construction and is safe, efficient and effective in use.